Sensitivity For Hg2 Research Articles

Surface Defects‐Induced Photoactivation of Carbon Dots‐NiFe2O4 Nanocomposite: Synthesis, Mechanism and Applications

AbstractThe optical properties of quantum dots are significantly influenced by photoactivation. However, the progress in the development of photoactivation carbon dot (CDs) is still stagnant. Herein, a method for preparing photoactivated CDs/NiFe2O4 by introducing affluent defects onto the surface of CDs through modification with NiFe2O4, extremely filling the gap of photoactivated CDs is proposed. Interestingly, a fantastic fluorescence detection strategy in a unique “OFF‐ON‐OFF” mode, combined with Ag+‐assisted fluorescence enhancement, to establish a dual‐channel regulation mechanism for ultra‐sensitive detection of Hg2+ is first proposed. By increasing surface traps and non‐radiative recombination, defect‐induced manipulation on the surface of CDs creates favorable conditions for enhancing photoactivation capacity. Unexpectedly, the CDs/NiFe2O4 shows a 25‐fold enhancement in fluorescence intensity after exposure to UV‐lamp. Compared to CDs/NiFe2O4, Ag+‐assisted photoactivation CDs/NiFe2O4 exhibits superior selectivity and sensitivity for Hg2+ detection, with low detection limits of 0.7 nM. Moreover, TiO2@CDs/NiFe2O4 catalyst is successfully prepared by anchoring CDs/NiFe2O4 onto the surface of TiO2, which demonstrates efficient degradation of tetracycline within 90 min under visible light irradiation, with a degradation rate of 98.3%. This work first provides a novel defects modification strategy for developing highly active photoactivated CDs technology that is significant for future environmentally sensitive applications.

Utilization of Schiff base ligands to chelate Ag+ for highly specific and sensitive Hg2+/Ag+ immunoassay

In this study, a planar benzothiazole Schiff base derivative ZX1 was designed and synthesized to selectively precipitate silver ions, in conjunction with the immunoassay detection of Hg2+ ions. The silver chelation process was highly effective in the pH range of 7–10, with a silver ion precipitation ratio of 99.9 %. The coordination behavior of ZX1 with Ag+ was studied using a series of spectroscopic measurements, topography analysis and DFT calculation. The shortest bond distances were 2.251 and 2.254 Å between nitrogen atom of thiazole and Ag+. Weak interactions were analyzed using the interaction region indicator (IRI) method and VMD. The immunoassay was developed through an anti-Hg2+/Ag+ monoclonal antibody, which showed similar sensitivities for Ag+ and Hg2+. The selectivity and anti-interference ability of the Schiff base ligands were tested for some hard metal ions and several anions. With co-existence of interference ion Ag+, Hg2+ was detected in rice matrix solution with 77 %∼123.5 % recovery by addition of ZX1 as the masking reagent and 90.3 %∼115 % for wheat matrix. This research provides a promising immunoassay strategy for simultaneous detection of silver ions and mercury ions in food matrix by utilization of Schiff base ligands. This novel Schiff base ligand was then used as the pre-treatment reagent to remove silver ions within 5 min for detection of Hg2+ or detection of both Ag+ and Hg2+ based on a novel bi-specific heavy metal antibody.

Molecular architecture of a novel indoline-fused chromenylium-cyanine probe carrying methionine biomolecule for ultrasensitive analyzing Hg2+ ion in real samples

In this study, by decorating the chromenylium-cyanine structure with an indoline ring, a new sensor platform CSI with a highly rigid structure and improved photophysical properties was developed for the first time. The CSI platform was modified with glyoxal and L-methionine methyl ester to produce a new NIR, ratiometric, and switch-on probe (CIME). This probe is biocompatible, water soluble, and has a specific binding mode for Hg2+ ion selectivity. The crystal structure of CSI was determined by x-ray crystallography, and its electronic characteristics, including HOMO-LUMO energy levels were determined by quantum mechanical calculations. CIME is the first instance of an indoline-fused chromenylium-cyanine used for quantification of trace level of Hg2+ in both the living cells and the environment. The new probe has a high level of selectivity and sensitivity for Hg2+ in aqueous media, with broad linear ranges (0–300 μM for UV-Vis and 0–225 μM for fluorescence). It has a rapid response time of 30 seconds, and UV-Vis and fluorescence detection limits of 7.4 ng/mL and 0.13 ng/mL, respectively. Probe quantitatively detected Hg2+ in real samples using UV-Vis, fluorescence spectrophotometry and a smartphone. The interaction between CIME and Hg2+ was verified by FTIR, HRMS and DFT calculations. Furthermore, the ability of CIME to sense Hg2+ in living cells was confirmed in both MCF-7 cells and 3T3 cells.

Advancements in on-site heavy metal detection: Characterizing and sensitive Hg2+ sensing of silver spheroid nanoparticles obtained by laser ablation synthesis in solution

Heavy metal detection in water bodies is crucial to prevent potential harm to the environment, animals and humans. While powerful techniques such as atomic absorption spectrometry exist, they often require extensive sample preparation and are typically confined to laboratory settings. As a result, alternative detection methods such as optical sensors, are under development to provide a simpler, faster, and on-site detection solution. In the present work spheroidal silver nanoparticles (AgNPs) with a mean size of 14.7 ± 0.6 nm were synthesized by laser ablation in a sodium citrate solution. These nanoparticles exhibit a localized surface plasmon resonance (LSPR), which is profoundly dependent on the size, morphology and composition of the nanoparticles and the refractive index of the surrounding media. The detection capabilities of these nanoparticles were assessed by exposing them to various metal ions, revealing a distinctive sensitivity to Hg2+ ions. Notably, this particular ion had a significant impact on the extinction curve of the AgNPs. The impact of synthesis parameters, including sodium citrate and NaCl concentration, as well as pH, on the efficacy of Hg2+ detection was systematically studied. Characterization techniques such as Dynamic Light Scattering (DLS), Transmission Electron Microscopy (TEM), High-Resolution TEM (HRTEM), and Scanning Transmission Electron Microscopy (STEM) were employed to determine the size, morphology, distribution, crystalline structure, and elemental composition of the AgNPs. The results indicated that AgNPs synthesized through laser ablation in a sodium citrate solution exhibited sensitive detection capabilities for Hg2+ ions, reaching an LOD and LOQ of 0.9355 μM and 2.8350 μM respectively.

Gold nanoparticle-enhanced D-shaped optical fiber sensor for mercury ion detection.

Mercury ions (Hg2+) are highly toxic heavy metal ions that pose serious health risks to humans when present at concentrations above the safety threshold. Therefore, the development of a rapid and effective Hg2+ detection method is of significant importance. In this study, based on surface plasmon resonance (SPR) technology integrated with COMSOL simulation analysis, a highly sensitive and selective Hg2+ sensing system is constructed. Initially, gold nanoparticles and the surface of a fiber-optic gold film are modified by sodium sulfide (Na2S). In the presence of Hg2+, the sulfur ions on the modified gold film and gold nanoparticles specifically bind to Hg2+, forming the composite structure Au/S-Hg2+-S/AuNPS. Due to the strong electromagnetic coupling between the gold nanoparticles and the gold film, a significant SPR wavelength shift occurs. These results show that the Hg2+ sensor has high sensitivity and enhanced selectivity. The detection limit for mercury ions was 8.15 nM, and the recovery rate in real environmental samples was up to 90.1-97.3%. This sensing system provides an alternative method for rapid and accurate determination of mercury content.

Ag nanoparticles incorporated metal organic framework (Ag@ZnBDC): Highly sensitive and selective detection of Hg2+ ions

Heavy metal ions (HMIs) pollutants pose remarkable hazards to humans and the environment. Their toxicity is a concern for both aquatic life and humans. HMIs directly threaten humans when consumed through drinking water or aquatic species such as fish. Therefore, detecting, quantifying, and removing these pollutants from water sources is necessary. In this study, we fabricated a highly selective and sensitive Hg2+ ion electrochemical sensor using a solvothermally synthesized composite of silver nanoparticles (Ag NPs) and zinc benzene dicarboxylate (ZnBDC) (Ag@ZnBDC) metal–organic framework (MOF) at trace levels. The synthesized Ag@ZnBDC MOFs composite was studied using various characterization techniques: structural, spectroscopic, thermal, Brunauer-Emmett-Teller surface area, morphological, elemental, and electrochemical techniques. The electrochemical sensor was fabricated by drop-casting the Ag@ZnBDC composite onto a glassy carbon electrode, and its sensing properties were evaluated using cyclic voltammetry and differential pulse voltammetry techniques. Remarkably, the sensor exclusively and highly selectively responded to Hg2+ ions among Cd2+, Cr3+, Cu2+, Fe3+, and Pb2+ ions at a concentration of 1 μM. The Ag@ZnBDC sensor showed a limit of detection of 4.16 nM in the linear response within the concentration range of 1–10 nM for Hg2+ ions.

A colorimetric and electrochemical dual-mode Hg2+ sensor utilizing oxidase-like activity arising from the combination of Hg2+ and palladium metal-organic framework@graphene.

Developingconvenient and reliable methods for Hg2+ monitoring is highly important. Some precious metal nanomaterials with intriguing peroxidase-like activity have been used for highly sensitive Hg2+ detection. However, H2O2 must be added during these detections, which impedes practical applications of Hg2+ sensors due to its susceptible decomposition by environmental factors. Herein, we discovered that the combination of Hg2+ and palladium metal-organic framework@graphene (Pd-MOF@GNs) exhibits oxidase-like activity (OXD). In the absence of H2O2, this activity not only catalyzes the oxidation of chromogenic substrates such as 3,3',5,5'-tetramethylbenzidine (TMB) or o-phenylenediamine (OPD) to produce a color change but also enhances the electrical signals during OPD oxidation. Based on these properties, an effective and convenient dual-mode colorimetric and electrochemical sensor for Hg2+ has been developed. The colorimetric and amperometric linear relationships for Hg2+ were 0.045μM-0.25mM and 0.020μM-2.0mM, respectively. Theproposed strategy shows good recovery in real sample tests, indicating promising prospects for multiple environmental sample detection of Hg2+ without relying on H2O2. The colorimetric and electrochemical dual-mode Hg2+ sensor is expected to hold great potentials in applications such as environmental monitoring, rapidfield detection, and integration into smartphone detection of Hg2+.

Collaboration strategy-based fluorescence sensor for efficient detecting Al3+ and Hg2+

Developing economical sensors and methods to efficiently detect metal ions like Hg2+ and Al3+ is still significant. Hg2+ is notorious for its strong neurotoxicity, while, Al3+ is a risk factor for Alzheimer's disease (AD) in humans. To improve the selectivity and sensitivity of Hg2+ and Al3+, in this research, the collaboration effect has been successfully applied to the design of chemosensors to enhance the detecting ability of the sensor. According to this strategy, quinoline-8-yloxy acetohydrazone and hydroxy‑naphthyl groups have been rationally introduced into one sensor molecule, based on the collaboration of these functional groups, the obtained chemosensor (QN) shows efficient “off-on-off” response for Al3+ and Hg2+. QN can ultra-sensitively detect Al3+ with fluorescent “turn-on” response, the limit of detection (LOD) of QN towards Al3+ is 4.34×10-9 M. Interestingly, after coordination with Al3+, the obtained complex QN-Al can detect Hg2+ sensitively, the LOD of QN towards Hg2+ is 5.70×10-8 M. The Al3+ and Hg2+ sensing process shows nice selectivity, and the detecting procedure cannot be interfered with by other common metal cations. The possible recognition mechanism of QN for Al3+ and Hg2+ was carefully investigated via experimental and theoretical studies. According to these studies, the selective and sensitive sensing of Al3+ and Hg2+ is based on the collaborative coordination of quinoline acetohydrazone and hydroxy‑naphthyl groups. The relay sensing procedure of Al3+ and Hg2+ is attributed to the competitive coordination of these two cations. The fluorescent response of Al3+ might be attributed to excited state intra-molecular proton transfer (ESIPT) and photoinduced electron transfer (PET), meanwhile, the Hg2+ response mechanism may be ascribed to the chelation enhancement quenching effect (CHEQ). Moreover, the detection of real samples is conducted to determine the aluminum content in food to prove that chemosensor QN is suitable for the detection of Al3+ from food samples, and the QN-based test kits for convenient detection of Al3+ and Hg2+ were also successfully prepared.

Naphthalimide-based fluorescent probe for Hg2+ detection and imaging in living cells and zebrafish.

A simple naphthalimide-based fluorescent probe was designed and synthesized for the determination of mercury ion (Hg2+ ). The probe showed a noticeable fluorescence quenching response for Hg2+ . When added with Hg2+ , the fluorescence intensity of the probe at 560 nm was remarkably decreased with the color changed from yellow to colorless under ultraviolet (UV) light. The probe had a notable selectivity and sensitivity for Hg2+ and displayed an excellent sensing performance when detecting Hg2+ at low concentration (19.5nM). The binding phenomenon between the probe and Hg2+ was identified by Job's method and high-resolution mass spectrometry (HRMS). Moreover, the probe was not only utilized to identify Hg2+ in real samples with satisfactory results (92.00%-110.00%) but also was successfully used for bioimaging in cells and zebrafish. The recognition mechanism has been verified by transmission electron microscopy (TEM) for the first time. All the results showed that the probe could be used as a potent useful tool for detection of Hg2+ .

Efficient sensitization of CdTe QDs towards PTCDA for sensitive photoelectrochemical Hg2+ assay.

Herein, a sensitive photoelectrochemical (PEC) biosensor was designed for the detection of mercury ions (Hg2+) on the basis of the efficient sensitization of cadmium telluride quantum dots (CdTe QDs) towards 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) and the significant quenching ability of a thymine-Hg2+-thymine (T-Hg2+-T) structure. The proposed CdTe QD/PTCDA sensitized structure was successfully constructed via continuous incubation of PTCDA and CdTe QDs on the glassy carbon electrode (GCE) interface, which embraced strong light absorption capacity and high carrier separation efficiency, giving rise to a remarkably improved initial photocurrent response. Notably, the PEC signal generated from the CdTe QD/PTCDA sensitized structure was almost fivefold higher than that of PTCDA owing to the efficient sensitization of CdTe QDs towards PTCDA. Once target Hg2+ ions were added, a T-rich S1 strand modified on the surface of 1-hexanethiol (HT)/S1/gold nanoparticles (Au NPs)/CdTe QDs/PTCDA/GCE immediately reacted with Hg2+ to produce multiple stable T-Hg2+-T structures. Therefore, the initial PEC signal would be considerably quenched by a high steric hindrance effect derived from the T-Hg2+-T structures. As a result, a quenched PEC response could achieve the detection of Hg2+ in concentrations ranging from 100 fM to 1000 nM. More importantly, the combination of the CdTe QDs/PTCDA sensitization structure and the T-Hg2+-T structure paves a promising pathway to developing a novel PEC biosensing platform for Hg2+ detection and also provides a favorable strategy for monitoring environmental pollution related to Hg2+.

Mercury-Mediated Epitaxial Accumulation of Au Atoms for Stained Hydrogel-Improved On-Site Mercury Monitoring.

Trivalent Au ions are easily reduced to be zerovalent atoms by coexisting reductant reagents, resulting in the subsequent accumulation of Au atoms and formation of plasmonic nanostructures. In the absence of stabilizers or presence of weak stabilizers, aggregative growth of Au nanoparticles (NPs) always occurs, and unregular multidimensional Au materials are consequently constructed. Herein, the addition of nanomole-level mercury ions can efficiently prevent the epitaxial accumulation of Au atoms, and separated Au NPs with mediated morphologies and superior plasmonic characteristics are obtained. Experimental results and theoretical simulation demonstrate the Hg-concentration-reliant formation of plasmonic nanostructures with their mediated sizes and shapes in the presence of weak reductants. Moreover, the sensitive plasmonic responses of reaction systems exhibit selectivity comparable to that of Hg species. As a concept of proof, polymeric carbon dots (CDs) were used as the initial reductant, and the reactions between trivalent Au and CDs were studies. Significantly, Hg atoms prevent the epitaxial accumulation of Au atoms, and plasmonic NPs with decreased sizes were in situ synthesized, corresponding to varied surface plasmonic resonance absorption performance of the CD-induced hybrids. Moreover, with the integration of sensing substrates of CD-doped hydrogels, superior response stabilities, analysis selectivity, and sensitivity of Hg2+ ions were achieved on the basis of the mercury-mediated in situ chemical reactions between trivalent Au ions and reductant CDs. Consequently, a high-performance sensing strategy with the use of Au NP-staining hydrogels (nanostaining hydrogels) was exhibited. In addition to Hg sensing, the nanostaining hydrogels facilitated by doping of emerging materials and advanced chem/biostrategies can be developed as high-performance on-site monitoring routes to various pollutant species.

A Semi-Automatic Environmental Monitoring Device for Mercury and Cobalt Ion Detection.

A syringe-based, semi-automatic environmental monitoring device is developed for on-site detection of harmful heavy metal ions in water. This portable device consists of a spring-embedded syringe and a polydimethylsiloxane (PDMS) membrane-based flow regulator for semi-automatic fix-and-release fluidic valve actuation, and a paper-based analytical device (PAD) with two kinds of gold nanoclusters (AuNCs) for sensitive Hg2+ and Co2+ ion detection, respectively. The thickness of the elastic PDMS membrane can be adjusted to stabilize and modulate the flow rates generated by the pushing force provided by the spring attached to the plunger. Also, different spring constants can drastically alter the response time. People of all ages can extract the fix-volume sample solutions and then release them to automatically complete the detection process, ensuring high reliability and repeatability. The PAD comprises two layers of modified paper, and each layer is immobilized with bovine serum albumin-capped gold nanoclusters (R-AuNCs) and glutathione-capped gold clusters (G-AuNCs), respectively. The ligands functionalized on the surface of the AuNCs not only can fine-tune the optical properties of the nanoclusters but also enable specific and simultaneous detection of Hg2+ and Co2+ ions via metallophilic Au+ -Hg2+ interaction and the Co2+ -thiol complexation effect, respectively. The feasibility of the device for detecting heavy metal ions at low concentrations in various environmental water samples is demonstrated. The Hg2+ and Co2+ ions can be seen simultaneously within 20 min with detection limits as low as 1.76 nm and 0.27 µm, respectively, lower than those of the regulatory restrictions on water by the US Environmental Protection Agency and the European Union. we expect this sensitive, selective, portable, and easy-to-use device to be valid for on-site multiple heavy metal ion pollution screenings in resource-constrained settings.

Multicolor Hg2+ sensor based on the regulation of peroxidase activity of Fe/Co-MIL-88(NH2) and etching of gold nanobipyramids

The entry of Hg2+ into the human body can lead to serious damage to some organs and it is vital to construct some simple but sensitive Hg2+ assay methods. A multicolor sensor for Hg2+ was constructed depended on the inhibition of peroxidase activity of Fe/Co-MIL-88(NH2) mediated by DNA and color change caused by the etching of gold nanobipyramids (Au NBPs). The enzymatic activity of Fe/Co-MIL-88(NH2) can be inhibited by adsorbing the T-rich oligonucleotide sequence on its surface. Hg2+ can combine with thymine of the T-rich oligonucleotide sequence to constitute T-Hg2+-T complex, and cause the transforming of T-rich oligonucleotide sequence into three-dimensional structure and desorbed from Fe/Co-MIL-88(NH2) surface. Which results in the restoration of the peroxidase activity of Fe/Co-MIL-88(NH2), and then it catalyzes the 3,3′,5,5′-tetramethylbenzidine (TMB) to engender TMB2+, TMB2+ can etch Au NBPs, this accompanied with a peak shift of the UV–vis spectrum and recognizable color changes of the system. Semi-quantitative can be realized using the multicolor changes of the Au NBPs as the reading mode. Furthermore, quantitative sensing can be achieved by measuring the UV–vis peak shift of the system. The linear response range is 1.0 nM–10 µM, and the detection limit (LOD) is 0.28 nM.

Highly fluorescent nitrogen-doped carbon dots derived from jengkol peels (Archindendron pauciflorum) by solvothermal synthesis for sensitive Hg2+ ions detection

A facile synthesis method involving a one-step solvothermal method is demonstrated in producing fluorescent nitrogen-doped carbon dots (N-CDs) by employing biomass waste (Jengkol peels) and ethylenediamine as a source for carbon and nitrogen. The synthesized N-CDs are spherical nanoparticles with an average size of 4.495 nm, exhibit solubility in water, emit bluish-green fluorescence and a high quantum yield of up to 42%. By using UV–Visible, FTIR, XPS, HR-TEM and Photoluminescence analysis, the as-prepared N-CDs were verified. We demonstrate that nitrogen doping increases fluorescence emission intensity to its radiative recombination of the π − π∗ transitions at CC and n − π∗ at CO or CN. an optimized excitation at 370 nm, the N-CDs exhibited strong PL emission at 522 nm. Under optimized conditions, N-CDs can be used to detect Hg2+ ions based on quenched fluorescence phenomenon. The result reveals excellent selectivity and sensitivity to Hg2+ ions with a detection range of 0.5 μM–4.5 μM. The resulting N-CDs may be used for detecting Hg2+ ions in cosmetics and tap water.

An enrichment-colorimetry integration strategy for nM-level Hg2+ detection in environmental waters based on an efficient Fe7S8-100 nanozyme and smartphone-based visual assay

A portable and highly sensitive Hg2+ colorimetric sensor was pioneered, in which Fe7S8-100 functioned as an efficient enrichment carrier and colorimetric catalyzer. Four types of Fe7S8-X (X = 0, 25, 50, 100) with varying pure phase compositions were fabricated by adjusting the ratios of ethylene glycol (EG) to water (H2O). The ultrapure Fe7S8-100 phase possessed superior catalytic activity and good enrichment ability. A Hg2+ detection sensor was constructed based on the pairing of Hg2+ with -SH in glutathione (GSH) using 3,3′,5,5′-tetramethylbenzidine (TMB) as the chromogenic substrate. The as-constructed platform provided a linear range (LR) of 0.01–300 μM with a detection limit of 3 nM. In addition, we developed a smartphone application (APP) for Hg2+ colorimetric assay with a detection limit of 30 nM and recovery of 86–115%. To maximize colorimetric sensitivity, an enhanced photography platform was fabricated to eliminate natural light interference and enhance photographic color intensity. Overall, the desorption-free, enrichment-colorimetry integration strategy, combined with smartphone visual detection, provides a practical solution for rapid, field monitoring of Hg2+ in environmental waters.

High sensitivity mercury ion fiber optic sensor based on Mach–Zehnder interference

This paper proposes a novel optical fiber sensor for highly sensitive Hg2+ detection based on Mach–Zehnder interference (MZI) structure and thiophene–chitosan hydrogel (TCH). We obtained the MZI structure by splicing the coreless fiber (CLF), thin core fiber, and CLF. And then, we etched the thin-core optical fiber cladding and assembled the TCH to produce a Hg2+ sensitive sensor. According to theoretical derivation and experimental verification, the detection sensitivity of the sensor to Hg2+ can reach 1.008 × 1011 mol l−1, and the detection limit is 5 × 10−13 mol l−1. The sensor also has performance stability within 24 h for concentration measurement, with an average standard deviation of 3.2 × 10−13 mol l−1 within an hour of observation. In addition, the sensor has the advantages of specificity, simple preparation, and low cost, and it is suitable for monitoring the concentration of Hg2+ in complex water systems.

Signal-on electrochemical aptasensor based on RGO-AuNPs and exonuclease-III with assistance of external probe for Hg2+ determination in shellfish

In this work, a signal-on electrochemical aptasensor, based on RGO-AuNPs and exonuclease-III (Exo-III), is introduced for sensitive Hg2+ determination in shellfish. RGO-AuNPs is one-step electrodeposited on screen-printed electrode (SPE) surface as a high-performance sensing platform. Hg2+ aptamer serves as a molecular recognizer and selectively responds to Hg2+, thus triggering thymine-Hg2+-thymine (T-Hg2+-T) coordination. Exo-III is activated to cleavage the T-Hg2+-T structure, leading to partial aptamer breakage on sensor surface. Particularly, the reduction of DNA phosphate skeletons actuates is sensitively recorded by the external signal probe (I[Fe(CN)6]4-) and further amplified, thus composing a signal-on system. Under optimum conditions, as-fabricated sensor presents a good linear relationship to Hg2+ level in the range of 3.5×10−3 – 5.6×10−1 mg L−1, and the detection limit (LOD) is well found as 1.2×10−3 mg L−1. In certified ICP-MS and recovery tests of shellfish samples, the errors and recovery rates are calculated as 1.5%∼4.4% and 97.5%∼103.5%, respectively.

Highly selective and sensitive detection of Hg2+ by a novel fluorescent probe with dual recognition sites

A novel thionocarbonate-coumarin-thiourea triad-based probe with dual recognition sites for sensing mercury (Hg2+) ion was developed. The synthesized probe possessed both fluorogenic (“off-on”) and chromogenic (from colorless to blackish brown) sensing performance towards Hg2+ ions. The fluorescence intensity was increased by 70 fold after the addition of Hg2+. As expected, the probe exhibited excellent selectivity and sensitivity for Hg2+ compared to other common competitive metal ions. The fluorescence intensity of the probe improved linearly with the increase of the concentration of Hg2+ (0–40 μM). Also, the minimum limit of detection (LOD) of the synthesized probe was 0.12 μM. Considering the importance of test feasibility in the harsh environment, the developed probe was applicable for detecting Hg2+ ions over a broad working pH range of 3–11. It is reliable and qualifies for the quantitative determination of Hg2+ concentrations in actual water samples. Finally, the probe achieved the bioimaging performance of Hg2+ in living cells and plants with good biocompatibility.

A Novel Pyrene-Based "Off-On" Fluorescent Probe with High Selectivity and Sensitivity for Hg2+

A Novel Pyrene-Based "Off-On" Fluorescent Probe with High Selectivity and Sensitivity for Hg2+

Synthesis of two nitrogen-doped carbon quantum dots to construct fluorescence probes for sensitive Hg2+ detection with dual signal output.

The rapid and sensitive detection of heavy metal ions is of great importance in food safety and for the environment. Therefore, two novel probes, M-CQDs and P-CQDs, based on carbon quantum dots were utilized to detect Hg2+ based on fluorescence resonance energy transfer and photoinduced electron transfer mechanisms. The M-CQDs were prepared from folic acid and m-phenylenediamine (mPDA) using a hydrothermal method. Similarly, the novel P-CQDs were obtained according to the same synthetic procedure used to create M-CQDs except the mPDA was replaced with p-phenylenediamine (pPDA). Upon the addition of Hg2+ to the M-CQDs probe, the fluorescence intensity reduced significantly with a linear concentration range between 5 and 200 nM. The limit of detection (LOD) was calculated to be 2.15 nM. On the contrary, the fluorescence intensity of the P-CQDs was enhanced greatly after the addition of Hg2+. The Hg2+ detection was realized with a wide linear range from 100 to 5000 nM and the LOD was calculated to be as low as 52.5 nM. The fluorescence "quenching" and "enhancing" effect exhibited by the M-CQDs and P-CQDs, respectively, is due to the different distribution of -NH2 in the mPDA and pPDA precursors. Notably, paper-based chips modified with M/P-CQDs were established for visual Hg2+ sensing, demonstrating the possibility for real-time detection of Hg2+. Moreover, the practicality of this system was confirmed through the successful measurement of Hg2+ in tap water and river water samples.